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Biomedical subjects

D J Etherington

Publications and source records attributed to D J Etherington.

At least 19 recordsLinked to original sources
PubMed1996

An ecological study of cancer incidence and radon levels in South West England.

To investigate the relationship of domestic radon levels and cancer, the incidence of 14 major cancers in Devon and Cornwall were examined in relation to the local radon levels. Cancer registrations for 1989-1992 were provided by the South-Western Regional Cancer Registry. The average radon levels for postcode sectors were sorted into ten categories from low (< 40 Bq/m3) to extremely high (> or = 230 Bq/m3) and age-standardised incidence rates were calculated for each radon category. The incidence rates for lung cancer, where radon has been claimed to be a risk factor, were very similar across all domestic radon categories. Only non-melanoma skin cancers, showed a significant increase in incidence in the high-radon postcode sectors (> or = 100 Bq/m3) compared with the low-radon sectors (< 60 Bq/m3) and this effect was observed for both sexes. The remaining 12 cancer sites showed no significant trend in incidence rates with increasing radon concentration. There was no significant difference in corrected survival rates for any cancer site between the low- and high-radon areas. The possible contribution of confounding factors to the results of this study is discussed.

England↗
PubMed1995

Uterine collagen during pregnancy in cattle.

Uteri were collected at the slaughter of non-pregnant dairy cattle and cattle at various stages of gestation. The weight of the whole uterus increased about 12-fold during the 9 month gestation period. The greatest increase was in the weight of the pregnant horn. The increase in weight of the uterine horns was accompanied by an increase in collagen content. The collagen concentration did not change. The collagen crosslink pyridinoline was identified in pregnant uterine tissues at a level of about 0.13 residues per mole of collagen; this level was the same at the beginning and end of pregnancy.

Amino Acids↗
PubMed1994

Improving the comparability of cancer registry treatment data and proposals for a new national minimum dataset.

BACKGROUND: There is no consistent or standardized practice for the collection of treatment data in UK cancer registries. This limits the usefulness and effectiveness of undertaking multiregional or national studies of treatment outcomes and survival. METHODS: A working group was established to examine the practices for recording the type and the amount of treatment data held in the cancer records at different registries. A common set of anonymized case notes for breast and colorectal cancer patients, drawn from each registry, was employed to eliminate any selection bias. Each registry coded these case notes according to their own criteria, and the comparability of such data between registries was determined from their returns. RESULTS: Of the 11 registries in England, seven participated in the full study, with a total of 84 records being submitted by five registries. A flow diagram was constructed to show how specific data items in the cancer record structure could be linked between registries. Errors or inconsistencies in recording treatment details were identified, and the constraints in data comparability were defined from the case note returns. CONCLUSION: Variations in coding practice between registries were such as to vitiate interregional or national comparisons of current data. The working group recommended an extended minimum dataset, which included a date for the start of each treatment modality, that most registries should be able to implement with some system changes.

Data Collection↗
PubMed1991

The effect of modification on the susceptibility of collagen to proteolysis: I. Chemical modification of amino acid side chains.

A series of chemically modified collagens were subjected to proteolysis by lysozomal cathepsins, pepsin and trypsin. Modifications of the collagens included acetylation, succinylation, methylation and borohydride reduction. Changes in the integrity of the materials were also monitored by differential scanning calorimetry (DSC). All modified collagens were implanted intramuscularly to assess their relative biodegradation rates in vivo. Methylation of the collagen showed extensive denaturation as confirmed by DSC, pepsin solublization to small fragments and by increased susceptibility to trypsin. However, methylation and succinylation made little difference to hydrolysis by cathepsins. Acetylation and borohydride reduction gave increased resistance to cathepsins as well as to pepsin, this latter also being found with the succinylated substrate. In-vivo implantation data showed both succinylation and methylation increased the rate of biodegradation but that the other modifications did not affect the rate of breakdown when compared with control unmodified collagen. The results of this study showed that chemical modification of collagen can alter in vivo degradation rates and could aid in designing collagen-based prostheses.

Acetylation↗
PubMed1991

Uterine collagen during involution in cattle.

Post-partum involution of the bovine uterus was assessed by clinical examination and monitored biochemically by measuring the total urinary excretion of hydroxyproline and the collagen cross-link, pyridinoline. Uterine tissue contained 0.13 +/- 0.04 residues of pyridinoline per mole of collagen and negligible (less than 0.005 residues/mole) deoxypyridinoline. The pyridinoline/creatinine ratio was found to be a clearer and more reliable indicator of uterine resorption than the hydroxyproline/creatinine ratio. The amount of collagen cross-link excreted above baseline was equivalent to the amount of cross-link estimated to have been accumulated during pregnancy. Maximal excretion of pyridinoline occurred at day 6 and returned to baseline values in 2-3 weeks after parturition. An electron microscope study during the period of peak resorption revealed macrophage-like cells apparently engulfing or containing collagenous material, indicating phagocytic removal of the connective tissue.

Amino Acids↗
PubMed1990

Susceptibility of the cartilage collagens types II, IX and XI to degradation by the cysteine proteinases, cathepsins B and L.

We have investigated the susceptibility of both the helical and non-helical regions of isolated rat chondrosarcoma collagens, types II, IX and XI, to degradation by the cysteine proteinases, cathepsins B and L. Both enzymes degrade these collagens at temperatures from 20 to 37 degrees C and pH values from 3.5 to 7.0. Cleavage occurs only within the non-helical domains unless the helix is destabilized. Cathepsin L is more effective than cathepsin B on a molar basis and they appear to cleave at different sites. Since these cathepsins can degrade cartilage collagens at pH values near neutrality, they may contribute to the destruction of cartilage observed in arthritis.

Cathepsin B↗
PubMed1989

Immunodetection of cathepsins B and L present in and secreted from human pre-malignant and malignant colorectal tumour cell lines.

Pre-malignant and malignant human colorectal tumour epithelial cell lines both secreted precursor forms of the 2 cysteine proteinases, cathepsins B and L. The amount of proteinases secreted by these cell lines varied according to the cell density. Comparison at similar cell densities showed that the pre-malignant, adenoma-derived cell line (PC/AA) secreted as much, or more, of both cathepsin B and L precursors as did the malignant, carcinoma-derived cell line (PC/JW/FI). However, mature forms of cathepsins B and L were detected in the culture media of only the carcinoma-derived cell line, thus indicating that the invasive potential of a tumour may be related to its ability to process extracellularly the secreted precursor enzyme to a mature and consequently active enzyme, rather than to the amount of proteinase synthesized and/or secreted. Similar results were obtained using 2 other epithelium-derived tumour cell lines, HT/29 (carcinoma) and SP/AN (adenoma). Immunolocation studies showed that cathepsin B was lysosomal while cathepsin L appeared to have a distribution more consistent with a plasma membrane association. Purified human cathepsins B and L (mature form) were capable of solubilizing an isolated basement membrane matrix (bovine anterior lens capsule) in vitro, thus indicating that the secreted mature enzymes and the membrane-associated cathepsin L could potentially degrade basal laminae or sub-endothelial basement membranes in vivo.

Adenoma↗
PubMed1988

A comparison of four cathepsins (B, L, N and S) with collagenolytic activity from rabbit spleen.

We have separated four cathepsins (B, L, N and S) from rabbit spleen. They are all collagen-degrading cysteine proteinases, with Mr values of 25,250, 23,500, 34,000 and 30,000 for cathepsin B, L, N and S respectively. Cathepsins B, N and S have isoelectric points of 5.4, 6.2 and 6.8 respectively, whereas cathepsin L exhibited multiple charge forms in the range 5.0-5.7. A comparison of their specific activity against a variety of protein and synthetic substrates shows many differences. These differences can be visually illustrated through isoelectric focusing and detection of enzymic activity with protein and synthetic-substrate overlays. By using an enzyme-linked immunosorbent assay based on the binding to chicken cystatin and detection with polyclonal and monoclonal antibodies to native cathepsins B and L, no cross-reactivity of the four native enzymes was observed. Studies on the co-operative or synergistic effect in degrading collagen indicated that, of the different combinations tested, only the combination of cathepsin B and N exhibited enhanced collagenolysis.

Animals↗
PubMed1988

Microelectrode studies on the acid microenvironment beneath adherent macrophages and osteoclasts.

Osteoclasts and activated macrophages in culture were shown to generate an acidic microenvironment specifically in the attachment zone between the cell and the base of the culture dish. Measurements using pH microelectrodes revealed that osteoclasts, when firmly attached, could achieve a pH fall of about 1 unit min-1 to a limit value of pH 3.0 or less. Activated macrophages produced a slower fall of 0.5-2 pH units h-1 and a limit value of pH 3.6-3.7 was generally detected. The method of activation was relatively unimportant, but where macrophages formed clumps the pH effect was reinforced. Osteoclasts were also examined in situ in osteoporotic bone fragments in rabbit ear chambers, using a combination H+ and Ca2+ double-barrelled electrode. The pH readings reached a lower limit of 4.7 and the calcium concentration rose to a maximum of 40 mM in the erosion sites. In vivo such acid conditions would favor the direct extracellular action of secreted lysosomal proteinases in the degradation of collagen by both cell types.

Animals↗
PubMed1988

Elevation of cathepsin L levels in the synovial lining of rabbits with antigen-induced arthritis.

The activity and distribution of the collagenolytic lysosomal enzyme, cathepsin L, has been assessed in the synovial lining of the rabbit during the initiation and development of chronic (antigen-induced) arthritis. Biochemical assay of homogenates of synovial lining revealed a marked increase in the activity of lysosomal enzymes, including cathepsin L, between 1 and 5 days following initiation of arthritis. Elevated levels of these enzymes were still present at 4 weeks duration of arthritis. Using a monospecific antibody to cathepsin L. enzyme was immunolocated only in synovial lining cells in normal joints. In arthritic joints the enzyme was found in synovial lining cells, synovial fibroblasts and in infiltrating macrophages. Measurement, by scanning and integrating microdensitometry, of the peroxidase-reaction product in synovial lining cells revealed an increased content of cathepsin L in these cells in the diseased tissues.

Acetylglucosaminidase↗
PubMed1987

The immunohistochemical location of cathepsin L in rabbit skeletal muscle. Evidence for a fibre type dependent distribution.

The immunohistochemical location of cathepsin L in rabbit soleus, plantaris and psoas muscles was investigated using the peroxidase-anti-peroxidase (PAP) technique. The amount of enzyme detected varied according to the fibre type, which were identified by histochemical staining of serial sections for succinate dehydrogenase and alkali-stable myosin ATPase. In the three muscles studied labelling was strongest in the highly oxidative fibres and weaker in the other fibre types with least staining in the fast white fibres. Immunoreactive cathepsin L appeared to be most concentrated at the periphery of muscle fibres, especially near to the nuclei, although some staining was seen throughout the fibres.

Adenosine Triphosphatases↗
PubMed1987

The influence of dissolved calcium salts on the degradation of hard-tissue collagens by lysosomal cathepsins.

Bone, calvaria and dentine collagens were incubated with crude preparations of lysosomal cathepsins obtained from liver, spleen and bone cells. Degradation was most rapid near or below pH 4 and the rate of degradation was increased two-to four-fold in the presence of 50-75 mM CaCl2. This concentration of Ca2+ ions was close to the saturating level of ions released from calcium hydroxyapatite in the pH range 3.5-4.0. Purified cathepsins B and L were very much less effective than the crude extracts in degrading the hard-tissue collagens. Cathepsin B was equally sensitive to the inclusion of 50 mM CaCl2 but cathepsin L activity was only slightly increased. The activating effect of Ca2+ ions was not specific as Mg2+ ions were equally effective. A partially-purified preparation of cathepsin N gave results similar to those obtained for the crude, mixed enzyme preparations. Spleen and bone cell extracts were much more effective than those of liver despite a lower content of cathepsins B and L. These findings suggest that a third enzyme, cathepsin N, which is known to be more abundant in spleen than liver, had contributed more of the collagenolytic activity in the spleen and bone cell extracts. Therefore in osteoclastic bone resorption the major collagen-degrading enzyme could be cathepsin N. Tendon collagen was degraded very rapidly by the crude and pure preparations of lysosomal cathepsins in the CaCl2-free buffers. However, when 50 mM CaCl2 was included in the incubation mixtures the reaction was strongly inhibited. The effect of the added CaCl2 appeared to be on the substrate since the activity of cathepsins B and L, was depressed by CaCl2 in the fluorimetric peptidase assays for these enzymes.

Animals↗
PubMed1987

Collagenolytic cathepsins of rabbit spleen: a kinetic analysis of collagen degradation and inhibition by chicken cystatin.

We have investigated the steady state kinetics of the degradation of native fibrillar collagen at pH 3.4 by four collagenolytic cathepsins of rabbit spleen. For each enzyme, the dependence of initial velocity on collagen concentration was well described by the Michaelis-Menten mechanism. Km, expressed as the concentration of triple-helical chains, and kcat values were determined for cathepsins B, L, N and S. The ratio of Kcat to Km suggest that cathepsins L and N are far more effective at collagen solubilization than either cathepsins S or B. Ki values were determined for the inhibition of collagenolytic activity at pH 3.4 using cystatin, a naturally-occurring cysteine proteinase inhibitor. All four cysteine proteinases were inhibited by cystatin in this assay system, although it was found to be a tighter binding inhibitor of cathepsin L, than for cathepsins N and S (approximately 5-fold less), or cathepsin B (approximately 500-fold less).

Animals↗
PubMed1986

Monoclonal antibodies to rabbit liver cathepsin B.

Three stable hybridoma cell lines (AF8, BC11, CE2) have been produced that secrete antibodies specific for cathepsin B. These have been characterized by ELISA, SDS-PAGE immunostaining, immunoprecipitation and immunofluorescent staining. CE2 immunoprecipitated native cathepsin B with retention of enzymic activity, but failed to cross-react with the alkali-denatured enzyme. BC11 bound only to the denatured form of cathepsin B and AF8 cross-reacted with both native and denatured cathepsin B. However, unlike CE2-immunoprecipitated enzyme, activity could be detected only after dissociation of the antigen-AF8 antibody complex. No cross reaction was found with any lysosomal protein including the cysteine proteinases, cathepsins H and L.

Animals↗
PubMed1985

Purification and immunological characterisation of two calcium-activated neutral proteinases from rabbit skeletal muscle.

Two Ca2+-activated neutral proteinases have been prepared to a high degree of purity from rabbit skeletal muscle. One, calpain I, is optimally activated by 100 microM Ca2+ and the other, calpain II, by 1 to 2 mM Ca2+. Both enzymes have two subunits of molecular weight 80 000 and 28 000. Antibodies have been raised against the native forms of both enzyme. It was found that the antibody to native calpain I reacted only with calpain I and not with calpain II, and similarly the antibody to native calpain II reacted only to calpain II. This suggested that the epitopes in the two enzymes are located in regions that are structurally different. However, immunoblotting of the denatured calpains after SDS-polyacrylamide-gel electrophoresis revealed cross-reaction between the two subunits for both enzymes. Therefore, although the denatured enzymes have common antigenic sites it would appear that these are not exposed equally in the native proteins.

Animals↗